The effect of the non-steroidal ecdysone agonist methoxyfenozide was evaluated against different developmental stages of the grape berry moth, Lobesia botrana Dennis & Schiffermuller (Lep, Tortricidae). Methoxyfenozide administered orally reduced the fecundity and fertility of adults treated with 1, 5 and 10 mg litre(-1); longevity was not affected. An LC(50) value of 4.5 mg litre(-1) was obtained when applied to eggs of less than 1 day old. Surface treatment was more effective than when applied by spraying. Administered into the diet, methoxyfenozide had a larvicidal effect; older larvae were more susceptible than younger larvae, with LC(50) values of 0.1 mg litre(-1) for L(1), 0.04 for L(3) and 0.02 for L(5). Larvae treated with sub-lethal doses throughout their lives did not emerge as adults at the highest doses (0.08, 0.04, 0.02 and 0.01 mg litre(-1)), with 65% and 40% emergence occurring for the lowest (0.005 and 0.0025 mg litre(-1)). Mortality occurred only in the larval stage.